Climate effects INCA-C New Papers PERSiST

Modelling DOC in the Canadian Sub-Arctic

Shanta Sharma recently defended her Masters thesis on modelling dissolved organic carbon (DOC) in the Canadian sub-Arctic. This was one of the most northerly applications of the INCA family of models and brought some unique challenges and insights.

The sub-Arctic in Canada and elsewhere is likely to experience hydroclimatic regime change associated with a rapidly changing climate. Simulations of landscape-scale carbon (C) budgets and pollutant transfer are needed by northern managers and stakeholders to understand and mitigate these possible impacts. The project simulated dissolved organic carbon (DOC) fluxes in a hydrologically complex watershed (Baker Creek) in the Northwest Territories. Discharge, DOC concentration, and DOC export were simulated PERSiST and INCA-C. The models were calibrated against available (2012-2016) discharge and DOC concentration data in sub-catchments of Baker Creek. The model successfully reproduced flow (R2: 0.87–0.94; NS: 0.82–0.91) and captured some aspects of DOC concentration dynamics (R2: 0.19–0.31).

Possible future conditions were simulated using two climate scenarios (elevated temperature (T), elevated temperature and precipitation (T+P)), and compared against a baseline scenario. Average discharge is projected to decrease under scenario T (22–27% of baseline) and increase (116–175% of baseline) under the T+P scenario. In this scenario, early winter increases in discharge suggest a change in hydroclimatic regime from nival to combined nival and pluvial. Future DOC fluxes are projected to decrease (24–27% of baseline) under scenario T and increase (64–81% of baseline) in the T+P scenario, with much of the increase in DOC export occurring during early winter. Any future increase in DOC export from Baker Creek may increase the mobility of previously deposited airborne metal contaminants, e.g., arsenic from Giant Mine.


Spatially explicit, landscape-scale modelling of GHG sources and sinks

Maria Holmberg and colleagues present an approach to collate spatially explicit estimated fluxes of GHGs (carbon dioxide, methane and nitrous oxide) for the main land use sectors in the landscape, and show how these fluxes can be aggregated to calculate net emissions of an entire region. They used INCA-C and PERSiST to estimate the flux of organic carbon from terrestrial ecosystems to lakes and rivers.

They developed and tested the approach in a large river basin in Finland, providing information from intensively studied eLTER research sites. To evaluate the full GHG balance, they included fluxes from natural ecosystems (lakes, rivers, and undrained mires) together with anthropogenic fluxes from agriculture and forestry. They quantified fluxes using an anthropogenic emissions model (FRES), a forest growth and carbon balance model (PREBAS), and literature values for emissions from lakes, rivers, undrained mires, peat extraction sites and cropland. Spatial data sources included CORINE land use data, soil map, lake and river shorelines, national forest inventory data, and statistical data on anthropogenic activities. Emission uncertainties were evaluated with Monte Carlo simulations. They summed the vertical fluxes of spatially explicit net emissions, disregarding the impact of lateral fluxes from terrestrial to aquatic ecosystems on the vertical fluxes.

Their model results showed that artificial surfaces were the most emission intensive land-cover class while lakes and rivers were about as emission intensive as arable land. Forests were the dominant land cover in the region (66%). The forest C sink decreased total emissions for the region by 72%. The region’s net emissions amounted to 4.37 ± 1.43 Tg CO2-eq yr-1, corresponding to a net emission intensity 0.16 Gg CO2-eq km-2 yr-1, and estimated per capita net emissions of 5.6 Mg CO2-eq yr-1. Using INCA-C and PERSiST, the amount of organic C leaching from mires, cropland, and forests to the watercourses was estimated to correspond to about 10% of the CO2 and CH4 emissions from land to air.

Although the landscape approach developed by Dr. Holmberg and colleagues opens opportunities to examine the sensitivities of important GHG fluxes to changes in land use and climate, management actions, and mitigation of anthropogenic emissions, there is still a need to extend the work to a fully integrated regional GHG budget, accounting for all lateral fluxes of C- and N-containing compounds.

INCA-C New Papers Uncategorized

DOC Futures in UK Uplands

Jae-young Lee and colleagues have published a novel study of possible future trends in dissolved organic carbon (DOC) concentrations in a UK upland catchment.

Over the past several several decades, rising DOC concentrations have been seen in European lakes and rivers. A number of mechanisms have been proposed to explain these trends, including climate change and recovery from acidification. Drier summers and wetter winters are projected in the UK, and this may affect DOC levels. Lee and colleagues modelled DOC in the headwaters of the River Severn. They explored the effect of changing climate and acid deposition on surface water DOC concentrations, including the “enzymatic latch” effect in peatlands during droughts. They simulated recent (1995–2013) rising trends in DOC.

They used a novel approach to simulate possible future climate. The model was run with climatic scenarios generated using the weather@home2 climate modeling platform and EMEP sulfate deposition scenarios for 1975–2100. They showed that rising DOC trends are likely to continue in the near future (2020–2049) and stabilize in the far future (2070–2099). Seasonality will also change, with a post-drought DOC surge in autumn months.